Cam operated switching apparatus



Feb. 11, 1969 A. w. HAYDoN ET AL CAM OPERATED SWITCHING APPARATUS United States Patent O 8 Claims ABSTRACT OF THE DISCLOSURE A cam operated contactor includes a pair of springmounted contacts having followers on their springs. The camming member comprises a disc between the two followers which has a groove on each face. The grooves are of varying depth and are arranged so that they jointly operate the contacts for a very short period of time.

Background of the invention In connection with mulitple circuits such as those used in telephony, or for other circuit applications, it often is desirable to provide repetitive or cyclical signals of a preassigned duration. One example of this is a telephone system wink signal. The wink signal, usually a light, is deenergized twice a second for a period of thirty milliseconds. One problem has been to open the circuit for only this very short predetermined interval.

Summary The present mechanism comprises a rotary member which serves as a contact operating cam having overlapping cam surfaces on its opposite faces. The contacts are operated for extremely short times. The term operated for the contact movement is intended to include the action of opening or closing. For the example chosen, the very short time is a closing.

The contact members face each other on opposite sides of the cam and are biased toward their closed positions, from which they are held by the cam for most of the time. The biasing force preferably is produced by springs of the cantilever variety which are anchored at their ends opposite the contacts. Cam followers comprising rollers are secured to each spring between its contact and anchor.

In a preferred embodiment, the cam is a uniform diameter disc which runs between the oppositely located followers so that they are spaced sufficiently for the contacts to remain open except for a short predetermined interval during which the followers ride toward each other on the camming surfaces. During this interval, overlapping `camming surfaces on opposite faces of the disc move the followers to coordinately close the contacts.

Each camming surface advantageously comprises an arcuate groove which is divided into three areas consisting of an intermediate constant depth area flanked by a short steeply sloped taper and a long gently sloped taper. The steeply sloped tapers on the two surfaces have a slight overlap. The arrangement is such that one follower gradually moves inwardly allowing its associated contact to approach the opposite mating contact. Then the follower for the mating contact moves abruptly inward on its short slope to quickly close the contacts. After an extremely short closure, the first follower rapidly moves outwardly on its short slope taper to quickly open the contacts.

Brie]c description of drawings Other objects and features of this invention will appear more fully and clearly from the following `description of an exemplary embodiment thereof, taken in connection with the appended drawings, in which:

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FIGURE 1 is a side view of switching apparatus in accordance with an illustrative embodiment of this invention with an enclosing cover removed and shown in phantom lines;

FIGURE 2 is a front view of the apparatus shown in FIGURE l;

FIGURE 3 is an enlarged edge View of the camming disc; and

FIGURE 4 is a development of the camming portion of the disc to show the relation of its parts.

Description of a preferred embodiment The switching apparatus shown in the drawings is used for closing pairs of contacts for a brief interval of time. Referring to FIGURES l and 2, the apparatus includes motor input terminals 10a and 10b and two contact assemblies 11 and 12 which are supported in stacked array on one side of a mounting plate 13. The terminals 10a and 10b are connected to a suitable A.C. power source (not shown) and lead through conductors 14 to an electric motor 15 on the opposite side of the mounting plate.

Each of the Contact assemblies 11 and 12 is provided with two exible cantilever springs 16 and 17 having roller type followers 16a and 17a, respectively, intermediate their ends. Opposed pairs of contacts 18a and 18b are mounted at the respective outer ends of the springs 16 and 17. These contacts are biased toward each other by the springs 16 and 17 but are normally spacd apart by a rotary cam disc 20. The disc 20 is positioned with its axis extending in a `direction parallel to the direction of movement of the contacts 18a and 18b and is interposed between the followers 16a and 17a of each of the contact assembies 11 and 12. The arrangement is such that the followers 16a and 17a of each assembly ride on opposite faces of the `disc adjacent its periphery. The followers for the assembly 11 are diametrically opposed to the followers for the assembly 12, for purposes that will become more fully apparent hereafter.

The cam disc 20 is supported on the side of the plate 13 opposite that adjacent the motor 15 and is `driven by the motor shaft at a contant speed, illustratively thirty revolutions per minute. As the disc rotates, the followers 16a and 17a for each of the assemblies 11 and 12 deflect their respective contact springs 16 and 17 to move the contacts 18a and 18h apart or allow them to close due to the effect of the bias in the springs. It will be noted that the switch assemblies 11 and 12 are alike except that their followers are reversely oriented to a-ccommodate opposite peripheral portions of the disc.

The cam disc 20, as seen in the enlarged view of FIG- URE 3, has camming surfaces or grooves 21 and 23 which are respectively disposed on the opposite faces of the disc. Each of the grooves 21 and 23 accommodates the corresponding followers 16a and 17a adjacent the periphery of the disc 20 and describes a circular arc which illustratively is of the order of about sixty-four degrees. As brought out more clearly in the developed view of FIGURE 4, each groove comprises three zones, 21-1, 21-2, 21-3, and 23-1, 23-2, 23-3. The zones 21-1 and 23-1 are short and make an angle of about thirty degrees with the corresponding disc face, while the zones 21-3 and 23-3 are long and make an angle of about two `degres with the corresponding face. Between these zones are the zones 21-2 and 23-2 which are essentially uniform in depth. In the illustrated embodiment, thefzones 21-1 and 23-1 form radial angles of approximatelyl four degrees, the zones 21-2 and 23-2 form radial angles of approximately nine degrees, and the zones 21-3 and 23-3 Aform radial angles of approximately fifty-one degrees.

It is apparent from FIGURE 4 that there is a slight overlap between the cam grooves 21 and 23 on the two faces of the disc 20. Thus, the zone 23-1 is opposite one end portion of the zone 21-2, and the zone 21-1 similarly is opposite one end portion of zone 23'-2. The zones of the respective grooves are reversed in their orientation such that, for a given direction of rotation of the disc 20, the zone 21-1 comprises the leading portion of the groove 21 while the zone 23-3 comprises the leading portion of the groove 23.

As a consequence of this overlapping arrangement, and with the cam disc moving in the direction of the arrow in FIGURE 4, each of the followers 17a: (FIGURE l) riding on the tapered cam surface 2`3-3 allows the biasing force from the associated spring 17 to gradually move the corresponding contact 18b toward the opposite contact 18a until the follower reaches the constant depth surface 23-2. Shortly before the follower 17a moves onto the surface 23-1, the cooperating follower 16a for the contact 18a rides down the steep slope of the surface 21-1 to allow the -biasing force from the spring 16 to abruptly close the contact 18a against the already positioned contact 18h. Immediately thereafter, the follower 17a follows the short steep slope of the surface 23-1 to abruptly move its contact 18b away from the contact 18a and thereby open the circuit. The follower 16a then rides along the surface 21-2 and up the gradual slope of the surface 21-3 to its initial position. To insure an extremely accurate timing interval, the points at which each pair of followers contact the disc are directly in a line parallel to the ldisc axis, and the amount of overlap of the cam surfaces is accurately adjusted in accordance with the desired interval.

By operating two pairs of contacts on diametrically opposite sides of the disc 20, a balanced arrangement is assured, although for many applications satisfactory operation is realized with but a single contact pair. The location of the cantilever springs of a Contact pair adjacent opposite faces of the disc has a beneficial balancing effect which helps to insure the rotation of the disc in a precise flat plane. Because one contact moves gradually toward the other one, which then moves quickly, bouncing of the contacts is minimized.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. Switching apparatus comprising a plurality of opposed spring members, a pair of facing contacts respectively mounted on said spring members, a cam follower on each spring member, and a cam between the followers, the cam comprising a rotatable disc of uniform thickness except for a camming surface on each face thereof, the camming surfaces being identical but being reversely arranged, each camming surface comprising a central portion anked by a portion having a long taper and a portion having a short taper, the orientation of the camming surfaces on the disc being such that they overlap sufciently to locate each short taper portion opposite the central portion of the opposing surface.

2. Switching apparatus as in claim 1 in which the cam 'followers contact the rotatable disc at points which are disposed along a line parallel to the axis of rotation thereof.

3. Switching apparatus as in claim 1 in which the angle of each short taper portion with respect to the cam disc is about and the angle of each long taper portion with respect to the disc is about 2.

4. Switching apparatus comprising a pair of flat elongated springs in spaced relation to each other, mounting means for supporting each spring adjacent one end thereof, the respective springs having mating contacts at their opposite ends, a roller secured to each spring between the mounting means and the corresponding contact, and

a uniform diameter camming disc rotatably positioned between the rollers, the rollers bearing on directly opposite areas of the disc faces, the overall thickness of the disc being sufcient to spread the springs and disengage their contacts, the opposite faces of the disc including grooves each -having a long and a short taper flanking a substantially uniform depth portion, the grooves overlapping by a small amount to allow the contacts to close for a few tens of milliseconds only.

5. A cam operated interval timing switch that comprises a pair of cantilever leaf springs having facing contacts thereon, a cam follower on each spring, a discshaped cam mounted for rotation between the followers and having camming areas on each face thereof, the springs biasing the followers against the opposite faces of the cam, the camming areas being identical in contour but reversely arranged, each camming area comprising a constant depth zone flanked by a zone having a long taper and another Zone having a short taper, the orientation of the zones being such that each of the short taper zones is opposite the constant depth zone of the opposing camming area, and means for rotating the cam.

6. A cam operated interval timer comprising a pair of spring members, facing contacts carried by said spring members, oppositely situated cam followers respectively mounted on said spring members, a cam disc between the followers and having its respective faces in contact therewith, the cam disc being of generally uniform thickness but having camming surfaces comprising grooves on opposite faces of the disc adjacent its periphery, each groove being made up of a uniform depth zone, a gently sloping zone and a steeply sloping zone and being oppositely arranged with respect to the other groove with the steeply sloping zone of each groove opposite `the uniform depth zone of the other groove, and means for rotating the cam disc.

7. Switching apparatus comprising a pair of flat elongated springs in spaced relation to each other, mounting means for supporting each of said springs adjacent one end thereof, the respective springs having mating contacts at their opposite ends, a rroller secured to each spring between the mounting means and the contact therefor, a uniform diameter camming disc rotatably carried between the rollers and including two grooves on its opposite faces, the rollers bearing on directly opposite areas of the disc faces within said grooves, the thickness of the major portion of the ydisc being suicient to spread the springs and disengage their contacts, each of said grooves having a short portion of substantially uniform axial depth flanked by tapered portions of variable depth, one of which is a long taper of several times the length of the uniform depth portion and the other of which is a short taper, the grooves overlapping slightly adjacent their short tapers such that the total duration of contact closure is a few tens of milliseconds.

8. Switching apparatus as in claim 7, in which a plurality of pairs of said springs, said contacts and said rollers is supported adjacent different sections of said disc with two pairs of said rollers respectively bearing on diametrically opposite sides of the discs axis of rotation.

References Cited UNITED STATES PATENTS 2,221,575 ll/ 1940 Clark 20G-153.11 2,555,801 6/1951 Mallory ZOO-453.11 2,760,018 8/1956 Spenard 20G- 153.14 2,811,700 10/1957 Kueh 200-l53.l4 3,359,392 12/1967 Heath 20G-'153.11

BERNARD A. GILHEANY, Primary Examiner.

HAROLD BROOME, Assistant Examiner. 

